Some links to other information about soil quality:

soilcare The overall aim of the EU funded SOILCARE project is to identify and evaluate promising soil improving cropping systems and agronomic techniques increasing profitability and sustainability across scales in Europe.
landmark LANDMARK is a European Research Project on the sustainable management of land and soil in Europe. The questions that LANDMARK aims to address are: “How can we make the most of our land ? How can we ensure that our soils deliver on the many expectations we have of our land ?”
 sq australia  Soil Quality Website Australia
 sq eh Soil Quality for Environmental Health 
PennState Soil Quality - Introduction to Soils

Healthy soils yield healthy crops, But what is healthy soil and how do we achieve it?

SH USDA

USDA - Natural Resources Conservation Service:

Healthy Soil for Life